Replaceable target sidewall insert with texturing

ABSTRACT

This invention provides a sputter target ( 30 ) and backing plate ( 60 ) assembly having a replaceable sputter target sidewall insert ( 10 ). The replaceable sidewall insert ( 10 ) enhances the effectiveness and useful life of the assembly by replacing only the insert portion of the sidewall ( 10 ) when needed, while retaining the remaining portions of the target ( 30 ) for additional use. The sidewall insert ( 10 ) is secured to the target ( 30 ) and backing plate ( 60 ) in corresponding grooves ( 66 ) provided in the target ( 30 ) and backing plate ( 60 ). A textured surface ( 16 ) such as a continuous textured coating may be applied to the sidewall insert ( 10 ) to further enhance particle retention properties of the target/backing plate assembly.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to target sidewalls, and in particular to areplaceable target sidewall with textured surface. Replacement of thetarget sidewall extends the life of the target and increases theretention of deposited material on the target sidewalls.

2. Description of Related Art

In typical sputtering processes, metal atoms, from a metal or metalalloy sputter target are deposited onto a substrate in a physical vapordeposition (PVD) atmosphere. Most of the sputtered metal atoms travel,as desired, directly to the substrate. However, a significant portion ofthe sputtered particles become scattered in the gas during the PVDprocess and can deposit on various unintended surfaces of the chamber,such as the shield, or the target itself.

The scattered sputtered particles that deposit onto the variousundesired surfaces of the sputter chamber such as the target sidewall,shield or other chamber component, tend to build-up and flake off duringlater sputtering processes. Deposition of scattered sputtered particleson the target is especially troublesome. For instance, the repeatedheating and cooling of the target, including the undesired depositedparticles on the sidewalls of the target, render flaking of theparticles even more likely.

In many cases, these particles are propelled to the substrate and causedeleterious results in the uniformity of the sputtered coating.Accumulation of particles onto the shield may be remedied by replacementof the shield. Heretofore, the target sidewall itself could not bereadily replaced.

Conventional targets were often provided with smooth sidewalls fromwhich the deposited particles would flake off easily and contaminate thechamber and the coating uniformity. In order to improve retention ofthese deposited particles, the sidewalls were often roughened by beadblasting. Later improvements included arc spraying to increase theroughness of the sidewalls even more. A portion of the target could alsobe made to overhang the textured surfaces of the sidewalls to furtherinhibit deposition of scattered particles on the sidewalls. All of theseprior art alterations were intended to improve the performance of thetarget, while inhibiting accumulation and improving retention ofundesirable deposit particles on the target, thereby increasing theuseful life of a target.

Target life time should be determined primarily by target thickness.However, in the case of N₂ reactive sputtering of Ti targets, the targetlife is often limited by accumulation of TiN deposits on the target,particularly on the sidewall portion.

The prior art approach of bead blasting has not proven totallysuccessful in eliminating flaking off of undesired particles,particularly TiN particles. For example, the amount of depositedmaterial cannot be held firmly by bead blasting and the embeddedblasting media itself may not hold the TiN at all and can actually serveas a particle generator. Arc spraying appears to be the bestalternative, but the undesirable TiN deposits must still be made toadhere to the target throughout its useful life.

Accordingly, there is a need in the art for an effective way in which areplaceable target sidewall may be provided so that it may be replacedalong with other normally replaceable system components such as shieldsand the like. Additionally, it is desirable to provide a replaceabletarget sidewall that is treated, as by texturing, to increase retentionof deposited particles thereon.

SUMMARY OF THE INVENTION

This invention provides a sputter target and backing plate assemblyhaving a replaceable sputter target sidewall insert. The replaceablesidewall insert enhances the effectiveness and useful life of theassembly by replacing only the insert portion of the sidewall whenneeded, while retaining the remaining portions of the target foradditional use.

This invention separately provides that the replaceable sidewall insertis fitted into a groove provided around the circumference of the targetand a corresponding groove in the backing plate. The sidewall insertcould thus be formed as a cross-sectionally L-shaped ring member fittinginto the respective, communicating grooves of the target and backingplate around the target/backing plate assembly.

This invention separately provides a sidewall insert removably fitted tothe target and backing plate, wherein the sidewall insert is comprisedof a textured surface. The textured surface enhances the retention ofparticles deposited thereon. The textured surface may be an arc sprayedsurface comprised of, for example, Al or Cu or alloys thereof and thelike. In all of the exemplary embodiments, the textured coating on thesidewall is selected to roughen or texture the surface to result in lessstress to the particles deposited thereon. The textured surface could beprovided by bead blasting, knurling, etching, machining or otherconventional means. Additionally, foamed metals can be used as thereplaceable sidewall insert. These materials themselves have texturedsurface by their very nature. Foamed Al, Ni, and Cu metals arecommercially available.

The sidewall insert could also be composed of a shaped memory metal suchas the various nickel-titanium alloys known in the art. These metals canbe “trained” to take on a predetermined shape in response to a stimulussuch as a change in temperature. For example, the trained state could bean expanded state or shape in which the insert could be readily removedfrom the target/backing plate assembly.

Also, the insert could be composed of a metal having a negativecoefficient of thermal expansion. For example, Zr and some Zr alloysexhibit this property upon cooling of the target/backing plate assembly,the Zr insert could be readily removed from the assembly in its relaxed,expanded state.

In various exemplary embodiments of the invention, the removablesidewall insert is a deep drawn L-shaped ring having a continuouscoating, wherein the ring is press fitted and friction fit in theassembly using spring tension from the ring against a lip, forming partof a groove on the target, and an outer wall, forming part of a grooveon the backing plate.

In still other exemplary embodiments of the invention, the removablesidewall insert comprises a ring having a pre-thinned area that aidsinstallation into the corresponding grooves of the target and backingplate. The pre-thinned area may simply be cut in order to facilitateremoval of the sidewall insert. A new removable sidewall insert may thenbe installed in place of the removed sidewall insert.

In all of the various exemplary embodiments of the invention, theremovable sidewall insert is removably secured to the target and/orbacking plate so that the sidewall insert can be removed and replacedwith another sidewall insert when the effectiveness of the precedingsidewall insert is exhausted due to meeting or exceeding a thresholdvalue of depositioned particles thereon. For example, double-sidedelectrically conductive adhesive tape may be used to secure the insertto the assembly, or screws may be used to secure the insert to theassembly. Other fastening devices such as bayonet mounts or ball detentmounts may be used to secure the insert to the assembly provided theremovable sidewall insert is easily attachable and removable from theassembly when desired.

In all of the exemplary embodiments the sidewall insert can be replacedas often as desired. For example, if desired, the sidewall insert can bechanged every time the shield of the sputter chamber is changed. In thismanner, the life of the target is increased as the shield of the sputterchamber and the target sidewall insert can be replaced whenever each, orboth, reach a minimum threshold value.

A tool specifically designed for inserting and removal of the sidewallinsert may be used to snap fit the insert in place in the variousexemplary embodiments described, and/or to cut or otherwise remove theinsert from the grooves of the target and backing plate of theinvention. The sidewall could be provided with serrated portionsextending axially at one or more circumferentially spaced locations. Atool could be inserted behind these to easily cut the sidewall tofacilitate easy removal from the target/backing plate assembly.

These and other features and advantages of this invention are describedin, or are apparent from, the following detailed description of variousexemplary embodiments of the systems and methods according to thisinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Various exemplary embodiments of the systems and methods of thisinvention will be described in detail with reference to the followingfigures, wherein:

FIG. 1 is a view in perspective, showing the unassembled replacementsidewall and target/backing plate assembly in accordance with theinvention;

FIG. 2 is a partial cross-sectional view of the replaceable sidewallinsert and target/backing plate combination, showing the replacementsidewall in its disposition prior to assembly;

FIG. 3 is a view similar to FIG. 2 showing the sidewall in its inserteddisposition in the target/backing plate groove; and

FIG. 4 is a view similar to FIG. 3 but showing an alternative embodimentof the replaceable sidewall in accordance with the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Turning first to FIG. 1, there is shown a replaceable target sidewallinsert 10 in the general shape of an annulus. The insert is adapted tobe placed around the circumference of the target in a target/backingplate assembly.

The sidewall insert includes an upstanding first leg member 12 and ahorizontally connected second leg 14 with the first and second legsbeing generally perpendicularly disposed relative to each other. Theouter surface 16 of the leg 12 is provided with a textured surface. Thistextured surface may be accomplished via conventional techniques, suchas bead blasting, knurling, etching, machining, or by using a foamedmetal as the member 10. At present, it is preferred to provide atextured coating via an arc spraying method. This textured coating maycomprise materials such as Al and Cu and alloys thereof.

The leg 14 is also provided with a face surface 18 that can be similarlytextured. The top portion of the leg 12 is shown by reference numeral 20and defines the vertical boundary of the sidewall insert 10. Similarly,the peripheral boundary of the sidewall insert is shown at surface 22.

Turning briefly to FIG. 4, there is shown one particular embodiment ofthe invention wherein a thinned portion 24 is provided at the vertexbetween legs 12 and 14. This prethinned section may be cut in thesidewall insert so as to increase the springiness or elasticity of theinsert to aid in removal and installation of the insert into the groovesthat are provided in the target and backing plate.

Turning back to FIGS. 1-3 there is shown a target 30 of the typenormally employed in cathodic sputtering systems to provide the desireduniform coating onto the substrate. The target comprises a sputtersurface 32 from which desired metal atoms are ejected in the sputteringprocess to deposit onto the wafer or the like that is disposed proximatethe anode in the system. The target comprises a lower surface 34 and asidewall 36 extending around the circumference of the target.

An upstanding groove 38 is provided in the sidewall 36, and a lip member40 protrudes radially outwardly from the target to form a mechanicalstop with the top portion 20 of the insert snugly received under the lipas shown. Note especially in FIG. 3 that the sidewall surface 42 of thetarget and the outer surface 16 of the replaceable target sidewallinsert provide a smooth, continuous, linear surface area.

Again, with respect to FIGS. 1-3, a backing plate of the typeconventionally employed is provided. Backing plate 60 comprises topsurface 62 adapted to form an interfacial joined surface with the lowersurface 34 of the target. An opposing lower surface 64 is provided onthe underside of the backing plate and is adapted for heat exchangecontact with a heat exchange medium, traditionally water. Thecircumferential top surface of the backing plate radially protrudingaway from the target is provided with an annular groove 66 thereinadapted for receipt of the second leg 14 of the insert therein. Thelateral, circumferential extremity 22 of the insert is snuggly receivedby the peripheral boundary 72 of the annular groove 66.

As shown best in FIG. 3, it is noted that the top surface 70 of theperimeter portion of the backing plate and the face surface 18 of thesecond leg of the insert provide a smooth, continuous, linear surface.Again, the face surface 18 of the sidewall insert is also preferablytextured in order to increase particle retention thereon.

The insert 10 may be snugly snap fit or the like into the communicatinggrooves formed in the target sidewall and backing plate top surface.Additionally, fasteners such as bayonet mounts and slots and balldetents as shown in U.S. Pat. Nos. 4,820,397 and 5,147,521 may also beused to promote fastening of the insert to the target/backing plateassembly.

As shown, the outer surface 16 of leg 12 is in contiguous alignment withthe target sidewall surface 42. The surfaces 42 and 16 define acontinuous, linear surface area in the embodiments shown.

Overall, the cross-sectional shape of the insert can be viewed as beingsubstantially L-shaped with the first and second legs of the insertoriented so as to form the substantial L-shaped cross section. Thesecond leg member 14 of the insert and specifically its face surfacethereof 18 forms a continuous surface with the perimeter surface portion70 of the backing plate.

While this invention has been described in conjunction with the variousexemplary embodiments described above, it is evident that manyalternatives, combinations, modifications and variations are apparent tothose skilled in the art. Accordingly, the exemplary embodiments of theinvention set forth above are intended to be illustrative, and notlimiting. Various changes can be made without departing from the spiritand scope of this invention.

1. In a sputter target/backing plate assembly of the type wherein saidsputter target comprises a sputtering surface, a target sidewallsurrounding said sputtering surface, a target bottom surface joined tosaid backing plate and a sidewall channel formed in said targetsidewall, a replaceable target sidewall insert, said target sidewallinsert adapted for snug receipt thereof in said target sidewall channel,said replaceable target insert comprising an outer sidewall surfaceadapted for contiguous alignment with said target sidewall, said outersidewall surface comprising a textured surface receptive to particleattachment thereto.
 2. Replaceable target sidewall insert as recited inclaim 1 wherein said target sidewall and said outer sidewall surface ofsaid replaceable target sidewall insert define a continuous linearsurface area.
 3. Replaceable target sidewall insert as recited in claim2 wherein said target comprises a lip substantially perpendicularlydisposed relative to said target sidewall and extending outwardly fromsaid target sidewall, said replaceable target sidewall insert adaptedfor snug, abutting engagement with said lip while disposed within saidtarget sidewall channel.
 4. Replaceable target sidewall insert asrecited hi claim 3, in the form of an annulus.
 5. Replaceable insert asrecited in claim 3 wherein said backing plate has a receipt groovetherein in substantially perpendicular disposition with andcommunicating with said target sidewall channel, said replaceable targetsidewall insert having a substantially L-shaped cross-sectionalconfigurational shape comprising first and second leg members orientedsubstantially perpendicularly to each other and forming saidsubstantially L-shaped cross-sectional configuration, said first legmember including said outer sidewall surface, said second leg memberhaving a face surface adapted for forming a continuous surface with saidbacking plate, said face surface also comprising a textured surfacereceptive to particle attachment thereto.
 6. Replaceable target sidewallinsert as recited in claim 1 wherein said outer sidewall surface of saidinsert is adapted for continuous, linear disposition alongside saidtarget sidewall.
 7. Replaceable target sidewall insert as recited inclaim 1 wherein said target sidewall insert comprises a thinnedcross-sectional area to aid in installation and removal of saidreplaceable target sidewall insert from said target/backing plateassembly.
 8. Replaceable target sidewall insert as recited in claim 5,wherein said textured surfaces of both said outer sidewall surface andsaid face surface of said insert are formed via arc spraying, beadblasting, etching, or machining.
 9. Replaceable target sidewall insertas recited in claim 5 composed of foamed metal.
 10. A target and backingplate assembly comprising: a target; a backing plate, the targetattached to the backing plate and forming an interface therebetween; anda removable member joining the target and backing plate at theinterface.
 11. The target and backing assembly of claim 10, wherein theremovable member includes a horizontal portion and a vertical portionjoined to form a substantially L-shaped removable member.
 12. The targetand backing assembly of claim 11, wherein the horizontal portion of theremovable member is fitted into a groove on the backing plate, thegroove comprising an outer wall, an inner wall and a floor, and thevertical portion of the removable member is fitted along a straightportion of the target extending away from the backing plate.
 13. Thetarget and backing plate assembly of claim 12 wherein the straightportion of the target ends in a lip projecting outwardly from the targetsubstantially parallel to the backing plate such that the verticalportion of the removable member abuts the lip when fitted to theassembly.
 14. The target and backing plate assembly of claim 12, whereinthe removable member is provided with a textured outer surface.
 15. Thetarget and backing plate assembly of claim 14, wherein the textured coatis applied by arc spraying.
 16. The target and backing plate assembly ofclaim 14 wherein said removable member is composed of a foamed metal.17. The target and backing plate assembly of claim 14 wherein saidremovable member is composed of a shape memory metal.
 18. The target andbacking plate assembly of claim 14 wherein said removable member is ametal having a negative coefficient of thermal expansion.
 19. The targetand backing assembly of claim 10, wherein the removable insert furthercomprises a pre-thinned area aiding installation and removal of theremovable insert from the assembly.
 20. A removable insert for use witha target and backing plate assembly, the removable insert comprising: avertical portion; a horizontal portion, the vertical portion joining thehorizontal portion; and a textured surface on the vertical andhorizontal portions, whereby the vertical portion is adapted foralignment with a sidewall of the target and the horizontal portion isadapted for alignment with a portion of an upper surface of the backingplate.
 21. The removable insert of claim 20, wherein the texturedsurface is comprised of a metal alloy.
 22. The removable insert of claim21, wherein the textured surface is applied by arc spraying.
 23. Theremovable insert of claim 20 wherein said insert is composed of a foamedmetal.
 24. The removable insert of claim 20, wherein a pre-thinnedportion joins the vertical portion and horizontal portion, thepre-thinned portion adapted to aid installation and removal of theinsert from the assembly.
 25. The removable insert of claim 20 whereinsaid insert is composed of a shape memory metal.
 26. The removableinsert of claim 20 wherein said insert is composed of a metal having anegative coefficient of thermal expansion.